Dual-process theories and methods emerging from basic research on decision, memory, social cognition, and neuroscience have much potential for scientifically resolving fundamental questions about HIV risk behavior and its link to drug use. Indeed, new approaches are necessary, because behaviors known to cause increased risk of HIV/AIDS are perplexing-- they persist in some individuals or populations despite devastating, widely known consequences. Many approaches have attempted to explain risk behavior through theories of rational or deliberate processes, for example, in which people weigh the pros and cons and make a decision, or through dispositional characteristics of personality, in which some people are simply predisposed. Although previous approaches have been valuable, they may miss some fundamental processes governing risk behavior. Particularly, they seldom answer why people engage in these behaviors even when the hazards are understood. A different approach applies the growing evidence across disciplines for at least two independent but potentially interacting systems or processes that govern risky decisions: an autonomous, implicit or automatic system and a more reflective or deliberate system. The research proposed in this application investigates each class of system in multiple ways, evaluating alternative theoretical models of dual-processes. As an example, the more automatic system may affect risk behavior because the content of associations in memory processed in this system lead to spontaneously activated biases in decisions in favor of pre-existing, strong associations, not in favor of more difficult to activate, learned facts about HIV risk. Another model in this framework suggests a "buffer interaction" process, in which adequate functioning of reflective systems may dampen the otherwise "free reign" of spontaneous associations on risky behavior. This project investigates these hypotheses and several alternatives in a population at known risk for the transmission of HIV: adult non- injection drug users. The project conducts refinements of assessments and initial evaluations of alternative models in [an efficient cross-sectional study] and comprehensive evaluation of alternative hypotheses in a [four]-wave [intensive] prospective study. An evaluation of these alternatives may be critical for improvements in interventions in this population, because the findings address fundamental processes that are seldom acknowledged in intervention efforts. PUBLIC HEALTH RELEVANCE: Risk behaviors that foster the transmission of HIV/AIDS are extremely common in adult non-injection drug users. Because little is known about the reasons for a link between illegal drug use and the behaviors that transmit HIV/AIDS in this population, this project studies some of the most likely causes of this linkage using validated methods from basic research. Understanding why drug users continue to engage in behaviors that transmit disease is critically important for future HIV prevention programs, which are quite feasible because of recent mandates for diversion interventions in drug offenders.